1. Field of Invention
This invention relates to method and apparatus for restoring communication in an optical ring-network.
2. Description of Related Art
Optical ring-networks, such as synchronous optical network (SONET) rings, are a predominant networking paradigm. Wavelength division multiplexed (WDM) optical ring-networks are particularly desirable because of their comparatively high communication capacity, versatility and restoration capabilities. Unfortunately, optical ring-networks, like other communication networks, are subject to occasional failures. While a variety of techniques are currently available to restore communication in a failed optical ring-network, conventional optical ring-networks rely on complex optical hardware to restore communication. As a result, optical ring-networks having restorative capability can be expensive and unreliable. Accordingly, new technologies to form optical ring-networks are desirable.
The invention provides exemplary methods and apparatus for forming optical ring-networks having relatively simple and inexpensive hardware. In various exemplary embodiments, an optical ring-network having a primary module, and a number of secondary modules connected by two fiber-optic rings is disclosed. By configuring the secondary modules to simultaneously transmit optical signals along a clockwise and counter-clockwise direction on a first fiber-optic ring, and further configuring the secondary modules to simultaneously receive optical signals from a clockwise and counter-clockwise direction on a second fiber-optic ring, an optical ring-network can be constructed such that, if the optical ring-network fails at a particular point, restoration can be performed by a single switching operation at the primary module.
Because this architecture requires only a single active component, a restorable ring-network that is both inexpensive and highly reliable can be manufactured. Other features and advantages of the present invention are described below and are apparent from the accompanying drawings and from the detailed description which follows.